Optical receiver and optical add/drop apparatus

Abstract

Signal light (at a wavelength λs), entered an input terminal from an optical transmission line, inputs a combiner through an optical amplifier. The combiner combines the output light of the optical amplifier and the probe light (at a wavelength λp) from a probe light source and applies them to an EA modulator. The EA modulator superimposes a waveform of the signal light on the probe light. An optical BPF transmits only the component of the probe wavelength λp in the output light of the EA modulator. A photodetector converts the output light of the optical BPF into an electric signal, and an amplifier electrically amplifies the output of the photodetector. A BPF extracts the clock component of the input signal light from the output of the amplifier and applies it to a driver. The driver pulsatively drives the probe light source at the same frequency with that of the clock signal from the BPF and adjusts its pulse phase so as to synchronize with the current pulse from the EA modulator. A laser light source generates a probe light pulse according to a driving signal from the driver.

What is claimed is:  
     
         1 . An optical add/drop apparatus comprising: 
 an input terminal connecting with a first optical transmission line;    an output terminal connecting with a second optical transmission line;    a drop light output terminal;    an add light input terminal;    a waveform equalizer for equalizing a waveform of input light;    a first optical coupler for applying the input light of the input terminal to one of the drop light output terminal and the waveform equalizer; and    a second optical coupler for applying one of light from the add light input terminal and the output light of the waveform equalizer to the output terminal.    
     
     
         2 . The optical add/drop apparatus of  claim 1  wherein the first optical coupler comprises an optical switch for selectively applying the input light of the input terminal to one of the drop light output terminal and the waveform equalizer.  
     
     
         3 . The optical add/drop apparatus of  claim 1  wherein the second optical coupler comprises an optical switch for selectively applying one of the light from the add light input terminal and the output light of the waveform equalizer to the output terminal.  
     
     
         4 . The optical add/drop apparatus of  claim 1  wherein the waveform equalizer comprises a wavelength converter and the wavelengths of the input light and the output light of the waveform equalizer are identical.